Education Minister Leighton Andrews’ grip on exam regulation in Wales has come under increasing scrutiny after it emerged GCSE grade boundaries had been changed without his knowledge.

Data obtained using the Freedom of Information (FOI) Act reveals Welsh Government officials first considered changes in methodology – which led to students in Wales receiving lower grades – as far back as January 13.

But in written evidence to the Assembly’s Children and Young People Committee, Mr Andrews said it was some seven months later – on August 15 – that he was made aware of the Welsh Government’s decision to approve the changes.

David Evans, Wales secretary for the National Union of Teachers (NUT), questioned whether the GCSE grading fiasco could have been avoided if the issue had been addressed sooner.

A brewing row over this year’s GCSE English language scores ignited in August when teachers across Britain raised concerns that exams had been marked too harshly.

Mr Andrews launched an investigation into Wales’ English language performance after figures revealed an alarming 4% dip in the coveted A*-C benchmark.

A report published by the Welsh Government in September found that new methodology used to award grades led to candidates from Wales being awarded lower marks than would normally be expected.

It blamed England’s exams regulator Ofqual for the discrepancy, believing its insistence on using Key Stage 2 (KS2) predictors to determine expected outcomes had impacted on Welsh scores.

The change meant pupils in Wales had been graded against prior attainment in England, though officials said it was “hard to justify continued resistance” when it became apparent there were more students sitting the exam across the border.

Although 95% of students in Wales sat the WJEC’s English language GCSE, more than 70% of the exam board’s total candidates for the qualification were in England.

On that basis, the Welsh Government said it reluctantly agreed a “compromise” with Ofqual in order to guarantee results were published on time.

An e-mail exchange between Ofqual’s acting director of standards Cath Jadhav(cor) and Cassy Taylor, head of general qualifications regulation in the Welsh Government, reveals using KS2 predictors was first floated on January 13.

E-mailing at 11.03am, Ms Jadhav said: “Data from 2011 show[s] that WJEC actually had more GCSE entries from England than from Wales. We are therefore minded to ask them to report against KS2 predictions for matched candidates above a certain threshold and/or where the entry is above a certain proportion of the total entry.”

Responding, Ms Taylor said: “Quite understand your point, would greater than 50% of candidature being based in England be the best starting point for each subject?”

It emerged last week that Mr Andrews had met with officials from the Welsh Government’s Qualifications and Learning Division 24 times between October 10 last year and August 22.

In his evidence, Mr Andrews states that: “On August 15 I met with officials to discuss, primarily, the forthcoming A-level results, but officials also briefed me on the events of the previous week in relation to GCSE English language and explained how it had been necessary to agree a compromise.”

Liberal Democrat education spokesman Aled Roberts said: “It is imperative that the minister provides answers... on why there was a seven month gap between his officials agreeing the changes with Ofqual and the minister being briefed with regard to the consequences on Welsh grades as a result of their actions.”

The Welsh Government said its opposition to the changes in methodology had been “well-documented” and its officials “repeatedly put” their concerns to Ofqual.

A spokesman added: “As the minister has said before, ministers only became involved in exceptional circumstances. The exceptional nature in relation to GCSE English only became apparent in August.”

He said that “at no point” in their early discussions with Ofqual did officials think using KS2 predictors would “have any significant impact on the outcomes for candidates in Wales”.

Mr Andrews, Ms Taylor and schools director Chris Tweedale is due appear before the Children and Young People Committee on Thursday to answer questions about the GCSE fiasco.